The motion of individual myocardial regions can be measured using cine MR velocity images. The precision of the trajectories depends on image noise and artifacts, particularly due to the inconsistent motion of the blood in the heart chambers. These flow-related artifacts can be reduced by decreasing the blood signal, for example using presaturation pulses. We investigated the effects of flow-related artifacts and presaturation pulses on the reproducibility of measured trajectories. Methods and Results In four normal volunteers, a mid-ventricular axial slice was imaged six times - three with and three without presaturation. The artifact content in the lateral wall, anterior wall and septum was assessed by measuring the standard deviation in regions of interest displaced in the phase-encoded direction from the corresponding structure. Without presaturation, the artifact level above the lateral wall was 1.8 times lower than that above the anterior wall and septum. The difference dissapeared when presaturation was used. Ten regions were then tracked in each data set, five in the left lateral wall which is generally free of artifacts and five in the anterior wall and the septum, where artifacts are strongest. Mean trajectories were calculated for each technique and region and the root-mean-squared deviation was calculated. The table below compares the rms values (f standard error) for the various techniques and anatomical areas. Discussion Artifacts from flowing blood significantly compromise the reproducibility of the measured trajectories. The reproducibility in regions with artifacts is significantly improved when presaturation is used. Presaturation pulses require an increase in the repetition time and underestimation of the trajectory. However, the greatly improved reproducibility justifies this trade-off.